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Quantifying Individual-Level Inaccuracy in Glomerular Filtration Rate Estimation : A Cross-Sectional Study.

TitleQuantifying Individual-Level Inaccuracy in Glomerular Filtration Rate Estimation : A Cross-Sectional Study.
Publication TypeJournal Article
Year of Publication2022
AuthorsShafi T, Zhu X, Lirette ST, Rule AD, Mosley T, Butler KR, Hall ME, Vaitla P, Wynn JJ, Tio MClarissa, Dossabhoy NR, Guallar E, Butler J
JournalAnn Intern Med
Date Published2022 08
KeywordsCreatinine, Cross-Sectional Studies, Cystatin C, Female, Glomerular Filtration Rate, Humans, Kidney Function Tests, Male, Middle Aged, Renal Insufficiency, Chronic

BACKGROUND: Although the population-level differences between estimated glomerular filtration rate (eGFR) and measured glomerular filtration rate (mGFR) are well recognized, the magnitude and potential clinical implications of individual-level differences are unknown.

OBJECTIVE: To quantify the magnitude and consequences of the individual-level differences between mGFRs and eGFRs.

DESIGN: Cross-sectional study.

SETTING: Four U.S. community-based epidemiologic cohort studies with mGFR.

PATIENTS: 3223 participants in 4 studies.

MEASUREMENTS: The GFRs were measured using urinary iothalamate and plasma iohexol clearance; the eGFR was calculated from serum creatinine concentration alone (eGFR) and with cystatin C. All GFR results are presented as mL/min/1.73 m.

RESULTS: The participants' mean age was 59 years; 32% were Black, 55% were women, and the mean mGFR was 68. The population-level differences between mGFR and eGFR were small; the median difference (mGFR - eGFR) was -0.6 (95% CI, -1.2 to -0.2); however, the individual-level differences were large. At an eGFR of 60, 50% of mGFRs ranged from 52 to 67, 80% from 45 to 76, and 95% from 36 to 87. At an eGFR of 30, 50% of mGFRs ranged from 27 to 38, 80% from 23 to 44, and 95% from 17 to 54. Substantial disagreement in chronic kidney disease staging by mGFR and eGFR was present. Among those with eGFR of 45 to 59, 36% had mGFR greater than 60 whereas 20% had mGFR less than 45; among those with eGFR of 15 to 29, 30% had mGFR greater than 30 and 5% had mGFR less than 15. The eGFR based on cystatin C did not provide substantial improvement.

LIMITATION: Single measurement of mGFR and serum markers without short-term replicates.

CONCLUSION: A substantial individual-level discrepancy exists between the mGFR and the eGFR. Laboratories reporting eGFR should consider including the extent of this uncertainty to avoid misinterpretation of eGFR as an mGFR replacement.

PRIMARY FUNDING SOURCE: National Institutes of Health.

Alternate JournalAnn Intern Med
PubMed ID35785532